Electrochemical removal of 1,2-dichloroethane and 1,1,2-trichloroethane from synthetic groundwater.

摘要

Two model chlorinated aliphatic hydrocarbons, namely 1,2-dichloroethane (DCA) and 1,1,2-trichlorethane (TCA), were investigated for their removal from synthetic groundwater using electrochemical method. Degradation of the two compounds was monitored by measuring changes in the total organic carbon (TOC) concentration during the reaction. Preliminary experiments, using stainless steel and graphite planar electrodes, demonstrated that graphite was unsuitable in terms of both its stability and efficacy in TOC removal. The stainless steel plate electrodes were more effective in degrading the compounds under different experimental conditions, such as varying initial TOC concentrations, chloride concentrations, conductivity of electrolyte and applied current density. The half-life method demonstrated that degradation followed a zero-order kinetics (i.e. removal process was independent of initial TOC concentration in the range of 25 mg L-1 to 100 mg L-1). The chlorides and applied current density had a major effect on the TOC removal rates. Under lower current density the instantaneous current efficiency of the TOC removal process was greater than that under higher current density. The electrolytic conductivity had no direct effect on the TOC removal rates, but it reduced the energy consumption by reducing the cell voltage. The reaction temperature affected the TOC removal significantly and was adequately modeled by the Arrhenius equation. A carbon mass balance showed an approximately 7 and 1% deficit at the end of the experiment for DCA and TCA respectively. The deficit observed in total carbon mass in the system could be due to the errors involved in the gas sampling for CO2 analyses. The closing of mass balance indicated that during electrolysis, DCA and TCA were oxidized completely to carbon dioxide and water. The results demonstrate that electrochemical degradation using stainless steel electrodes could be used to remove chlorinated aliphatic hydrocarbons from an aqueous solution.